1. Field of the Invention
The present invention relates to an ink jet printer. The present invention also relates to a method of wiping an ink discharging plane.
2. Description of the Related Art
Ink jet printers are well known. An ink jet printer has an ink jet head. The ink jet head has an ink discharging plane. A plurality of ink openings is formed on the ink discharging plane. Ink is discharged from these ink openings toward a print medium. In this way, text and graphics will be printed on the print medium.
When ink is discharged from the ink openings for printing, the ink may adhere to the ink discharging plane. In addition, the ink may adhere to the ink discharging plane when processes which recover the ink discharging ability of the ink jet head, such as a purging process, a flushing process, or the like are performed. Viscosity of the ink adhered to the ink discharging plane will increase over time. This high viscosity ink sometimes closes the ink openings. When closed ink openings are present, ideal printing results cannot be obtained. Because of this, a wiper that will wipe off the ink adhered to the ink discharging plane is sometimes used. An operation of the wiper wiping the ink discharging plane will be hereinafter referred to as a “wiping operation”.
Japanese Patent Application Publication No. 9-52373 discloses an ink jet printer having a wiper. This ink jet printer adopts a carrier jet type. That is, a plurality of ink openings for discharging ink toward a print medium and a plurality of liquid openings for discharging dilution liquid are formed on an ink discharging plane of an ink jet head. One liquid opening is located adjacent to one ink opening. The dilution liquid discharged from each liquid opening dilutes the ink discharged from each ink opening. Ink diluted with the dilution liquid adheres to the print medium. This ink jet printer can change density of ink adhering to the print medium by adjusting an amount of the discharged dilution liquid. In this ink jet printer, the ink openings are formed on one end side of the ink discharging plane, and the liquid openings are formed on the other end side of the ink discharging plane. While the wiper is in contact with the ink discharging plane, it will move from the other end side to the one end side along the ink discharging plane. In this way, the wiping operation is performed. The dilution liquid may be discharged from the liquid openings when the wiper faces the liquid openings during the wiping operation.
In the ink jet printer of this conventional technology, a distance between the liquid opening and the ink opening located adjacent to the liquid opening is extremely small because it is required that the dilution liquid discharged from the liquid opening is mixed with the ink discharged from the ink opening. This distance is smaller than the distance between two adjacent ink openings.
When a wiping operation is performed by means of a wiper, ink that has been wiped off from the ink discharging plane will adhere to the wiper. Viscosity of the ink adhered to the wiper will increase over time. When a next wiping operation is performed by the wiper with the high viscosity ink, the ink on the wiper may be pushed into the ink openings. In this situation, ideal printing results cannot be obtained because the ink openings will be closed by the ink.
In the aforementioned conventional technology, the dilution liquid may adhere to the wiper during the wiping operation. The dilution liquid may dilute the ink adhered on the wiper. It seems that the ink on the wiper isn't pushed into the ink openings because the ink on the wiper is diluted with the dilution liquid. However, research by the present inventor has made it clear that even if low viscosity liquid is supplied to high viscosity ink adhered to the wiper, the ink on the wiper cannot be diluted to viscosity that is so low that the ink openings will not be closed. Even if the high viscosity ink adhered to the wiper is diluted, ink having medium viscosity will remain on the wiper. The present inventor discovered that, in the ink jet printer of the aforementioned conventional technology, the ink openings will become closed by the medium viscosity ink remaining on the wiper.